Extend LAP optimisations to more operations

Extend LAP optimisations to more operations

Extend the set of eligible opcodes for certain peephole
transformations, which then provide further optimisation
opportunities.

* lisp/emacs-lisp/byte-opt.el (byte-optimize-lapcode):
Optimise empty save-current-buffer in the same way as we already
do for save-excursion and save-restriction.  This is safe
because (save-current-buffer) is a no-op.
(byte-compile-side-effect-and-error-free-ops): Add list3, list4 and
listN.  These were all apparent oversights as list1 and list2 were
already included.
(byte-after-unbind-ops): Add stack-ref, stack-set, discard, list3,
list4 and listN.  Stack manipulation is safe because unbind cannot
read or modify stack entries.